Bath for metal pickling processes



Patented July 19, 1932 UNITED STATES PATENT OFFICE GEORGE L. HAGOUN, OF NITRO, WEST VIRGINIA, ASSIGNOB TO THE RUBBER SERVICE LABORATORIES OOMPANLOF AKRON, OHIO, A CORPORATION OF OHIO BATH FOB METAL PICKLTNG PROCESSES No Drawing.

The present invention relates to the art of cleaning metallic surfaces, and particularly to an inhibitor, which is added to an acid pickling bath to prevent undue attack upon the surface of a metal.

In the art of pickling, the metal is treated with a dilute acid to remove oxides such as rust, scale and other deposits, after which the metal is washed with water and dipped into an alkaline bath to remove the last traces of free acid. The acid ,removes the rust and scale, but unfortunately, from the pickling standpoint, unless some agent to prevent such action is present, it attacks the cleaned metal itself, thereby causing loss of metal and producing an evolution of hydrogen gas, which escapes into the air, carrying with it a fine spray of the acid liquor from the pickling bath and producing an atmosphere possessing corrosive properties and one which is injurious to health and damaging to equipment.

By the present invention, these objectionable features of the pickling process are substanti ally overcome or reduced to a minimum. Other objects of the invention are: to obviate embrittlement and pitting of the articles treated; to prolong the effective life of the pickling bath; and particularly to facilitate and increase the efficiency of the pickling operation. The objects of the invention, as herein set forth, are accomplished by adding to the pickling bath a regulating agent or inhibitor which acts to restrain the acid from attacking clean metal, but does not prevent removal of the rust, scale and other deposits.

In the examples hereinafter set forth for carrying out the metal pickling process, conditions were imposed which duplicated, so far as possible, those commonly followed in commercial practice, so far as concerned acid concentrations and temperatures employed.

The pickle regulator or inhibitor, as disclosed in the resent application, qo mppi sps a reaction r0 3 %....cf. a...gaaniding 19p9up, ifii'd fiilia erthstsea d ea hea bisatfidejff Uiiiiiethod by which one example of the preferred new class of inhibitors, namely a carbon bisulfide derivative of a reaction prod- Application filed September 80, 1931. Serial No. 566,169.

uct of diphenylguanidine and formaldehyde, was prepared follows: Substantially one molecular proportion of diphenylguanidine and substantially one-half a molecular proportion of formaldehyde, preferably in the form of a substantially 35% aqueous solution, were heated in the presence of a volatile organic solvent, preferably ethyl alcohol, to a refluxing temperature and maintained at that temperature until reaction was completed. An excess over one-half a molecular proportion of carbon bisulfide was added and a refluxing temperature was again maintained until the further reaction was completed. The solvent employed and any water present were removed from the product by any convenient means, as for example by evaporation. The residual product was a brittle resin at ordinary temperatures. The product may also, if preferred, be prepared without the use of an organic solvent.

The value of the above described product as an inhibitor was determined in the following manner: A steel test piece, substantially 3" x 4" in dimension, cut from 30 gauge hot rolled tin plate stock, exposing approximately 24 square inches of surface and weighing 16.866 grams, was immersed for 40 minutes in 750 c. c. of a water solution of sulfuric acid, containing approximately 6% by weight of 66 B. acid, to which had been added 0.047 grams of the inhibitor above described. The temperature of this bath was maintained at 8085 C. After being pickled in the manner described, the test piece was found to weigh 16.855 grams, showing a loss of onl 0.011 grams, or 0.00046 grams per square inc of surface exposed. A similar test piece weighing 18.499 grams and treated in the same manner, but without the use of any inhibitor, lost 0.519 grams, or 0.02163 grams per square inch of surface exposed. Thus it 1s shown that when the carbon bisulfide derivative of the reaction product of diphenylguanidine and formaldehyde is employed as an inhibitor, the loss in weight per square inch of surface exposed is only 2.1% as great as results if no inhibitor is employed in the pickling process. A greater saving in metal losses results from the use of a larger amount 100 the product,

of inhibitor than that employed in the example. Moreover, the steel plates pickled in the presence of the inhibitor set forth are clean and not stained upon removal from the pickle bath.

Other carbon bisulfide derivatives of a reaction product of a guanidine compound and an aldehyde have been prepared and tested as inhibitors in a pickling bath in the manner hereinbefore described. Thus, the following compounds were prepared and tested in this manner. Except as otherwise stated, the following compounds were prepared in a manner analogous for the preparation of derivative of the reaction product of phenlyguanidine and formaldehyde, except that in the case of other aldehydes than formaldehyde a substantially pure aldehyde, not an aqueous solution, was used. The molecular proportions of reactants used, however, were: substantially one of a guanidine compound, substantially one of aldehyde and substantially one-half of carbon bisulfide.

Compound A.-Carbon bisulfide derivative of the reaction product of guanidine and heptaldehyde. In this case, guanidine was used in the form of the carbonate, and sufficient strong alkali, for example, sodium hydroxide, was added to convert the guanidine carbonate into guanidine. At the end of the refluxing process, the alkali carbonate formed was separate from the solution of referably by filtration. .-Carbon bisulfide derivative of the reaction product of biguanide and benzaldehyde. This compound was preared in a manner similar to that employed in the preparation of compound A, except that in this case no solvent was used.

C'ompoumi C.-Carbon bisulfide derivative of the reaction product of phenyl-ortho-tolylguanidine and furfural.

Compo'w D.-Carbon bisulfide derivative of the reaction product of triphenylguanylthiourea and crotonaldehyde. No solvent was used in this case. e mixture of triphenylguanyl-thiourea and crotonaldehyde was heated at approximately 90 to 95 C. After addition of the carbon bisulfide, the

Compound mixture was refluxed in the usual manner.

C'om E .-Carbon bisulfide derivative of the reaction product of triphenylguanidine and acetaldehyde.

Uompmmd F .-Carbon bisulfide derivative of the reaction product of diphenylguanidine and acetaldehyde.

The results of the tests obtained on immersing steel test strips of 30 gauge hot rolled tin plate stock, 3" x 4 in dimension, for 40 minutes in 750 c. c. of 6% by weight of 0., in the presence of the indicated quantity of one of the above described inhibitors, are given in the table.

Table Weight w gm wags o! Weigh} of loss in ct o 5 area grams per k gg g inhibitor strip strip square p employed before after inch of pickling pickling exposed It is apparent from the data set forth that the preferred class of materials constitutes an important and highly efficacious group of inhibitors, as in all cases wherein one of the preferred inhibiting compounds was incorporated in the pickle liquor there resulted a great saving in the loss in weight of the steel test strips as compared with that resulting when no inhibitor was employed.

As a further example of the preferred class of inhibitors, there was prepared the carbon bisulfide derivatives of the reaction product of dicyandiamide and formaldehyde. This compound was tested in the manner hereinbefore described and found to possess the inhibiting qualities of the preferred class of compounds.

Other examples of the preferred class of inhibitors may be prepared by reacting other aldehyde derivatives of a guanidine comound than those described above with caron bisulfide. Thus, for example, the butyraldehyde derivatives of diphenylguanidine, triphenylguanidine, methylguanidine, biguanide and the like, the acetaldehyde derivatives of di-ortho-tolylguanidine, dicyandiamidine, aminoguanidine and the like, the formaldehyde derivatives of guanidine, phenyl-biguanide, triphenylguanidine and the like, the benzaldehyde derivatives of diphenylguanidine, phenylguanidine and the like, and many other analogous compounds may be reacted with carbon bisulfide and the products thus obtained employed as inhibitors in the manner hereinbefore set forth.

Other modes of employing inhibitors of the class hereinbefore set forth in the acid pickling of metals are apparent to those skilled in the art to which this invention pertains. The products described additionally may be employed in the presence of foaming agents, ionizable substances or other materials ordinarily used. Again, other acids than sulfuric acid may be employed in the pickle bath. Thus, hydrochloric acid as well as other substantially non-oxidizing inorganic acids may be employed in the pickle bath in conjunction with the preferred class 1oz. COMPOSITIONS,

1,868,214 3 of inhibitors in the manner hereinbefore set 9. A process of pickling iron and steel forth. products which comprises subjecting the What is claimed is: metal to be pickled to the action of a sulfuric 1. A process of pickling a metal which comprises subjecting the metal to be pickled to the action of a substantially non-oxidizing mineral acid solution containing a small proportion of a carbon bisulfide derivative of a reaction product of an aldehyde and a compound containing the grouping 2. A process of pickling a metal which comprises subjecting the metal to be pickled to the action of a substantially non-oxidizing mineral acid solution contaimng a small proportion of a carbon bisulfide derivative of a reaction product of an aldehyde and a guanidine.

3. A process of pickling iron and steel products which comprises subjectin the metal to be pickled to the action of a su furic acid solution containing a small proportion of a carbon bisulfide derivative of a reaction product of an aldehyde and a compound containing the grouping 4. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a carbon bisulfide derivative of a reaction product of an aldehyde and a guanidine.

5. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a carbon bisulfide derivative of a reaction product of an aldehyde and an aryl substituted guanidine.

6. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a carbon bisulfide derivative of a reaction 7. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a carbon bisulfide derivative of a reaction product of an aliphatic aldehyde and a phenyl substituted guanidine.

8. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a carbon bisulfide derivative of a reaction product of an aliphatic aldehyde and diphenylguanidine.

acid solution containing a small proportion of a carbon bisulfide derivative of a reaction product of formaldehyde and diphenylguani- 10. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a material formed by reacting substantially one-half a molecular proportion of formaldehyde with substantially one molecular proportion of diphenylguanidine and further reacting the product thus formed with substantially one-half a molecular proportion of carbon bisulfide.

11. A pickling bath for metal products which comprises a substantially non-oxidizing mineral acid solution containing a small proportion of a carbon bisulfide derivative of a reaction product of an aldehyde and a compound containing the grouping 12. A pickling bath for metal products which comprises a substantially non-oxidizing mineral acid solution containing a small proportion of a carbon bisulfide derivative of a reaction product of an aldehyde and a guanidine.

13. A pickling bath for iron and steel products which comprises a sulfuric acid solution containing a small proportion of a carbon bisulfide derivative of a reaction product of Examiner an aldehyde and a compound containing the.

17. A pickling bath for iron and steel products which comprises a sulfuric acid solution containing a small proportion of a carbon bisulfide derivative of a reaction product of an aliphatic aldehyde and a phenyl substituted guanidine.

. 18. A pickling bath .for iron and steel products which comprises a sulfuric acid solution containing a small proportion of a carbon bisulfide derivative of a reaction product of an aliphatic aldehyde and diphenylguanidine.

19. A pickling bath for iron and steel products which comprises a sulfuric acid solution containing a small proportion of a carbon bisulfide derivative of a reaction product of formaldehyde and diphenylguanidine.

20. A pickling bath for iron and steel products which comprises a sulfuric acid solution containing a small proportion of a material formed by reacting substantially one-half a molecular proportion of formaldehyde with substantially one molecular proportion of diphenylguanidine and further reacting the product thus formed with substantially onealf a molecular proportion of carbon bisulfide.

In testimony whereof, I hereunto afiix my signature.

GEORGE L. MAGOUN. 

